The present invention relates to oil and gas excavation, and in particular it relates to methods for oil and gas recovery from oil and gas containing layers in previously used wells.
It has been determined that main recovery of oil and gas from communicating pores in rock constitutes not more than 25%. It is determined by the presence of a normal layer pressure, a degree of water accumulation, and other causes. In complex collectors the number of communicating pores does not exceed 20%. The main quantity of oil and gas is contained in closed pores. However oil and gas actually are not recovered from them. Also with a drop in layer pressure and water inflow a well actually stops delivery of oil and gas
The known currently used method of opening, for example a cumulative perforation, can serve as an indicator of the presence of oil or gas, but not as a reliable method of opening in such collectors. It has been found that with the use of cumulative perforation, blocking water barriers are created, and thery prevent penetration of oil or gas into a well. This is confirmed by a decrease of productivity more than 6 times with an increases of number of cumulative perforation blasts. In conventional collectors there are 40-60% of such closed pores.
With the use of cumulative perforation microcracks are created along a dimension of a, which during a subsequent hydro-fracturing are increased and connected with water-containing spaces. This in turn leads to water overflow of a productive layer and subsequent stopping of oil or gas recovery
It is therefore desirable to use improved methods for recovery from productive layers significantly greater quantities of oil and gas, instead of abandoning the areas of oil and gas recovery after some quantities thereof have been recovered.